Atomic layer deposition (ALD) is a deposition technique used for the deposition of material layers over features formed on substrates. One example of an ALD process includes the sequential introduction of pulses of gases. For instance, one cycle for the sequential introduction of pulses of gases may contain a pulse of a first reactant gas, followed by a pulse of a purge gas and/or a pump evacuation, followed by a pulse of a second reactant gas, and followed by a pulse of a purge gas and/or a pump evacuation. Sequential introduction of separate pulses of the first reactant and the second reactant may result in the alternating self-limiting absorption of monolayers of the reactants on the surface of the substrate and, thus, forms a monolayer of material for each cycle. The cycle may be repeated to a desired thickness of the deposited material. A pulse of a purge gas and/or a pump evacuation between the pulses of the first reactant gas and the pulses of the second reactant gas serves to reduce the likelihood of gas phase reactions of the reactants due to excess amounts of the reactants remaining in the chamber.
However, the inventors have observed that some ALD processes undesirably produce high particle contamination of the substrate. The inventors believe that the particle contamination is resultant from deposition of materials on chamber components exposed to the process chemistry and that have direct line of sight to the substrate. To minimize or eliminate the particle contamination, more frequent cleaning of the affected chamber components would be required, undesirably resulting in a very short mean time between cleaning (MTBC) of these chamber components.
Therefore, the inventors have provided improved apparatus and methods for ALD processing of a substrate.